This application relates generally to turbine engines and, more particularly, to methods and apparatus for assembling turbine engine components that are fabricated from ceramic matrix composite materials.
Turbine engines include at least one stator assembly and at least one rotor assembly. At least some known rotor assemblies include at least one row of circumferentially-spaced rotor blades. The blades extend radially outward from a platform to a tip. A plurality of static shrouds coupled to a stator block abut together to form flowpath casing that extends circumferentially around the rotor blade assembly, such that a radial tip clearance is defined between each respective rotor blade tip and the casing or shroud. The tip clearance is tailored to be a minimum, yet is sized large enough to facilitate rub-free engine operation through the range of available engine operating conditions.
During operation, tip leakage across the rotor blade tips may limit the performance and stability of the rotor assembly. However, during operation, because the shrouds may be subjected to higher operating temperatures than the stator block, the shrouds may thermally expand at a different rate than the stator block or the fastener assemblies used to couple the shrouds to the stator block. More specifically, the differential thermal expansion may undesirably cause increased tip leakage as the operating temperature within the engine is increased. In addition, over time, the heat transfer from the shrouds and the differential thermal expansion may also cause premature failure of the fastener assemblies.
Accordingly, to facilitate reducing tip leakage caused by the differential thermal expansion, at least some known engines supply increased cooling flow past the shrouds and fastener assemblies. However, excessive cooling flow may adversely affect engine performance. To facilitate increasing the operating temperature of the engine, and thus facilitate improving engine performance, other known stator assemblies have included shrouds fabricated from stronger or higher temperature capability materials. However, although such materials should enable the shrouds to be exposed to higher operating temperatures, the operation of the engine may still be limited by the increased thermal differential expansion rates between the shrouds and the stator block through the fastener assemblies.